The invention relates to venting and pressure relief caps utilized for automotive vehicle tanks having fill necks. More specifically the present invention relates to drive mechanisms which translate rotation of a cap shell to independently operate a vent valve and rotatable closure member to secure the cap shell to the fill neck of the vehicle gas or coolant system tank.
The invention further provides for a lost motion drive connection for the closure drive to insure opening of the vent valve prior to uncoupling of the cap from the filler neck.
Previous cap designs have involved cumbersome drive mechanisms which required multiple parts and overlapping drive paths for the vent valve and closure drive. An example of such cap designs can be found in my U.S. Pat. Nos. 4,676,390 of Jun. 30, 1987 and 4,887,733 issued Dec. 19, 1989. Here the drive path for the vent valve includes part of the drive structure utilized for the closure function. Additionally these prior inventions require a drive hub, race, plunger, closure member and retainer mechanism to transmit rotary motion of the cap shell to both the vent valve and the closure device.
It is an object of this invention to provide a reliable pressure relief venting cap utilizing but a few part and with separate drives for the vent valve and closure securing mechanism.
It is a further object of the invention to provide sequential timing between the vent valve operation and the cap closure operation.
It is a still further object of the invention to provide a torque over-ride for the cap to minimize the possibility of damage to the closure mechanism from rotating the cap shell too much.
Additionally, the invention takes advantage of utilization of screw threads to provide for an effective sealing between the closure mechanism and the filler neck. This is advantageous since screw thread necks are easily installed and removed and also provide excellent sealing advantages. Use of screw threads advance the cap uniformly onto the filler neck. In this environment the old method of venting a cap by turning to vent and then pushing down for further rotation to uncouple the cap from the filler neck cannot occur, since screw threads prohibit downward pushing of the cap.
The closure means is a two portion closure. One portion grips the threads of the filler neck in a sealing manner to secure the cap to the filler neck while the other portion overlies the opening in the filler neck.
Since gas and coolant system tanks are pressurized due to expansion of tank contents and depressurized due to contraction and/or loss of tank contents, caps must be able to accommodate positive and negative changes in pressure. It is desirable of course to allow for some tank pressurization without venting to the atmosphere. This is true both to keep volatile fuel hydro-carbons from contaminating the air people breathe as well as to avoid loss of engine coolant. Accordingly, the invention contemplates a pressure relief assembly that does not open until user safety necessitates excess pressure relief. Likewise, the invention limits opening upon vacuum conditions to necessary operating tank pressure vacuum release conditions.
Because of safety conditions, the invention inhibits cap removal prior to venting of the tank. This not only insures that both the tank contents and cap will not spray or fly off into or against the hand and body of the person removing the cap, but also reduces the force necessary to remove the cap.
To this end the invention provides that initial attempts to remove the cap causes venting of the excess pressure prior to any rotation or release of the cap and the filler tank closure mechanism.
This is obtained through a lost motion connection between the cap shell and the closure device wherein initial removal rotation of the cap shell first vents the filler neck and that only after venting does continued rotation of the cap shell cause the closure means to rotate so as to be separable from the filler neck.
It is also an object of the invention to provide a torque responsive over-ride between the cap shell and the rotatable closure in order to insure that the closure member is not overstressed. This torque responsive over-ride takes place through a free wheel ratchet and a lost motion drive between the shell and the closure member. Excess torque will cause the free wheel drive to ratchet and allow the cap shell to rotate freely of the closure mechanism and thus prevent over stressing of the closure mechanism. The ratchet vibrations provides an indicator to the person tightening the cap that the cap is fully secured.
To provide ease in use the rotary motion that is used to release the closure mechanism is also utilized to actuate the vent valve. The invention obtains an axial shifting of the vent valve upon initial rotation of the cap shell. Once opened, the vent remains open to insure full venting prior to rotation of the closure mechanism to remove the sealing closure.
Because the free-wheel torque responsive mechanism allows for continued rotation of the cap shell even though the sealing closure is not rotated, an interlock has to be provided to insure that the vent valve retains its closed position during tightening. To this end the invention contemplates relative rotation between a vent valve actuator and the cap shell to cause actuation of the vent valve.
The invention also contains a drive mechanism for the vent valve actuator to cause it to rotate with the cap shell to avoid the aforesaid relative rotation and thus any further vent valve movement under torque overload conditions while the cap shell continues to rotate. This enables the vent valve to retain its closed position upon cap free wheeling and thus the user does not have to be concerned with the actual position of the cap in a closed position, since the vent will remain closed.
It is still a further object of the invention to pre-arm the vent valve to insure that initiation of any reverse cap shell rotation always opens the vent valve prior to rotation of the closure mechanism. Thus a user does not have to concern itself with any alignment of the cap shell in the closed position.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.